title: Disturbed sensory perception of changes in thermoalgesic stimuli in patients with small fiber neuropathies.
abstract: The assessment of functional deficits in small fibre neuropathies (SFN) requires using ancillary tests other than conventional neurophysiological techniques. One of the tests with most widespread use is thermal threshold determination, as part of quantitative sensory testing. Thermal thresholds typically reflect one point in the whole subjective experience elicited by a thermal stimulus. We reasoned that more information could be obtained by analyzing the subjective description of the ongoing sensation elicited by slow temperature changes (dynamic thermal testing, DTT). Twenty SFN patients and 20 healthy subjects were requested to describe, by using an electronic visual analog scale system, the sensation perceived when the temperature of a thermode was made to slowly change according to a predetermined pattern. The thermode was attached to the left ventral forearm or the distal third of the left leg and the stimulus was either a monophasic heat or cold stimuli that reached 120% of pain threshold and reversed to get back to baseline at a rate of 0.5 °C/s. Abnormalities seen in patients in comparison to healthy subjects were: (1) delayed perception of temperature changes, both at onset and at reversal, (2) longer duration of pain perception at peak temperature, and (3) absence of an overshoot sensation after reversal, ie, a transient perception of the opposite sensation before the temperature reached again baseline. The use of DTT increases the yield of thermal testing for clinical and physiological studies. It adds information that can be discriminant between healthy subjects and SFN patients and shows physiological details about the process of activation and inactivation of temperature receptors that may be abnormal in SFN.
authors.affiliation: Department of Neurology, Hospital Clinic, Barcelona, Spain Institut d'Investigació Augustí Pi i Sunyer, Facultat de Medicina, University of Barcelona, Barcelona, Spain Neurology Service, EMG Unit, Hospital de Clinicas, Porto Alegre, Brazil Neurology Service, Hospital Joan XXIII, Tarragona, Spain.
authors.forename: Conrado
authors.initials: C
authors.lastname: Medici
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Barraza
authors.forename: Carlos D
authors.initials: CD
authors.lastname: Castillo
authors.forename: Merche
authors.initials: M
authors.lastname: Morales
authors.forename: Pedro
authors.initials: P
authors.lastname: Schestatsky
authors.forename: Jordi
authors.initials: J
authors.lastname: Casanova-Mollà
authors.forename: Josep
authors.initials: J
authors.lastname: Valls-Sole
mesh_terms: D000328:Adult; D000368:Aged; D003080:Cold Temperature / Q000009:adverse effects; D004916:Erythromelalgia / Q000175:diagnosis* / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000379:methods* / Q000523:psychology; D017288:Pain Threshold / Q000502:physiology* / Q000523:psychology; D013697:Thermosensing / Q000502:physiology*; D055815:Young Adult
keywords: Dynamic thermotest; Neuropathic pain; Overshoot sensation; Psychophysical testing; Small fiber neuropathy; Thermal thresholds